The Distributed Process Control System of the Future? Inside ExxonMobil’s Patent Application

The interoperability of process control systems has been a largely philosophical debate, up until this point, but tangible examples of interoperability may soon be on their way. In August of 2015, several industry experts worked to design and filed a patent application: METHOD AND SYSTEM FOR MODULAR INTEROPERABLE DISTRIBUTED CONTROL. The patent application centered on a distributed control architecture and fundamental building blocks called Distributed Control Nodes (DCNs), which are field edge devices capable of control, running applications, and other functions. The patent applicants assigned the patent to the ExxonMobil Research and Engineering Company.

Relatedly, the DCN concept has been presented in many forums as part of the Open Systems Architecture Vision by ExxonMobil’s Don Bartusiak and others. These presentations promoted The Open Process Automation Forum standardization, part of The Open Group. With a group of ExxonMobil personnel and industry experts, the inventors and patent applicants include some prominent names in the process industry, including Dennis Brandl of BR&L Consulting and Dick Caro of CMC Associates. The full list of patent applicants & inventors includes:

About the Patent: The Abstract

A review of the patent reveals the following abstract which discusses the purpose of the invention:

METHOD AND SYSTEM FOR MODULAR INTEROPERABLE DISTRIBUTED CONTROL

A distributed control system (DCS) for controlling an industrial process using a plurality of distributed control nodes (DCNs) can include a plurality of Device DCNs, each Device DCN including an I/O interface coupled with a field device for single channel input or output, a plurality of Application DCNs, and one or more Ethernet switches. The plurality of Device DCNs and the plurality of Application DCNs can be adapted to host a software runtime and communicatively coupled via the one or more Ethernet switches. The DCS architecture can include of two types of DCNs; Application DCNs and Device DCNs. The software runtime can be configured to selectively provide control application level communication and function block execution services.

About the Patent: The Goals

The architecture is fundamentally an open system architecture which, according to the patent application, is designed to achieve the following goals:

As disclosed herein an interoperable open architecture based on industry standards can provide:

More technological innovation

Reduced system procurement and lifecycle cost

Increased incentives and a lower barrier to entry for new market entrants (e.g. small scale startups)

Reduced component development fine

Low-cost integration of new or improved components, allowing the addition of new functionality or replacement of obsolete components without significant cost barriers

Obsolescence and maintenance upgrade will be open to competition as the original supplier will not have a monopoly on future integration

Component interoperability through common data models and service bus technology allows applications to share both services and data

Portability of software achieved through the use of an industry standard language allows the code to be moved between different compiler-hardware-operating system environments. This allows a central engineering organization to adopt a build-once, use-everywhere strategy and a manufacturing facility to readily share code with other facilities even if they use different systems.

Use of industry standard network communication protocol to reduce the complexity of connecting and/or replacing third party devices and/or systems.

The disclosed subject matter's utilization of modular general purpose computing can provide for opportunistic upgrading without the cost hurdle associated with migrating field wiring and porting applications. This can open up the control network to high horsepower advanced multivariable applications that require either high frequency measurements or high availability. Accordingly, the disclosed subject matter can provide a scalable system that can incrementally grow processing capacity with the size and complexity of the manufacturing facility.

Additionally, in accordance with the disclosed subject matter, modular, single-channel I/O with control and application processing capability can provide the following benefits:

Can be mounted in a marshalling area in place of "dumb" terminal blocks and significantly reduce the number of expensive redundant general purpose controllers, equipment room "real estate" and ancillary equipment (e.g. HVAC, power, UPS, etc)

Eliminates the need for complex and costly redundancy schemes (except for the most critical of loops) through single loop integrity so that no individual processor failure can affect more than one regulatory control loop.

Allows a field project's I/O to be added at very low incremental cost, thereby increasing the project's rate-of-return

Allows any controller to read from or write to any I/O regardless of where it is physically connected into the system. This effectively makes traditional marshalling rack cross-wiring a virtual software exercise which translates into faster, lower-cost control system installation and lifecycle flexibility (although certain architectures designed to tightly limit scope of failure will introduce more system latency).

Eliminates wholesale DCS replacement projects in favor of treating the replacement and upgrade of modular components as a standard maintenance activity (much lower cost and far less operationally disruptive).

About the Patent: Details

The official patent is labelled accordingly, and can be found in multiple locations.

Patent Details

Patent Family ID: 1000001532444

Application No.: 14/826343

Filed: August 14, 2015

The application can be viewed here and can also be found with a little extra effort on the government patent website. Simply perform a search using the application number: 14/826343

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Bill’s Review

Having read the full patent, I highly advise reading the whole application to gain the full scope of the system, but here are some of the highlights that caught my eye in my reading:

DCN

The fundamental building block of the architecture are the Distributed Control Nodes (DCN) devices. A DCN incorporates a system-on-chip with an embedded operating system to coordinate and execute device applications and runtime software. DCNs execute control programs based on a number of industrial control standards, including IEC 61131-3, IEC 61499 and Foundation Fieldbus function blocks. Interestingly, the patent also describes potential facility to create function blocks with general purpose programming languages including. but not limited to, FORTRAN, Basic, C, c++, C#, and Java.

The Application DCN can host the centralized, advanced applications of the DCS. Any operating system that can host the DCN Service can be used as an Application DCN. Further, any computing platform, physical or virtual, is usable so long that it can host the Application DCN's operating system.

Global I/O Access

As for I/O access, any controller can access I/O within the system network directly using tag names. This is not a new feature in the industry. Incumbent vendor systems support this within their closed network, configuration software, and tag methods today. However, this closed ecosystem essentially limits the practical application of multi-vendor controllers on a project, because configurations are complicated, unreliable, and create performance issues.

Existing PLC & DCS Controller Interface

Likewise, existing PLC and DCS controllers can be brought into the new system architecture by connecting them to a Gateway DCN, which normalizes them to the open system architecture. Incumbent vendors also commonly use this type of interface strategy today. The big difference for these vendors, however, is that other devices are normalized to the vendor’s highly gated and proprietary architecture, unique to the vendor. This creates the same complicated, unreliable performance issues that interoperability is designed to solve. It does not have to be this way.

The joint PLCopen and OPC Foundation working group created an interoperability standard, including function blocks, in 2013 for controller-to-controller communications using common data models. Currently, the Technical Specification "OPC UA Information Model for IEC 61131-3," version 1.00, is only supported by a limited number of PLC vendors, who embrace PLCopen and OPC UA standards embedded in controllers and edge devices.

Final Thoughts & Observations

This patent application is clearly another expression of an open system concept and it references multiple open standards. These standards exist today to help spur the goal of creating open multiple vendor interoperable systems, but, thus far, users have not specified/demanded open systems or made purchase decisions which support open architectures.

There are other initiatives working to accomplish open interoperability in the industry as well. Hopefully we will see these efforts converge rather than diverge, leading to full interoperability and enhanced production for all.